Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Derrick R. Dean, Selvum Pillay, Alan M. Shih. Includes bibliographical references (p. 80-83).

The quasi-static strength, stiffness, and fatigue properties of cross-ply, angle-ply, and quasi-isotropic vinyl ester/E-glass non-woven tricot stitched fabric composite laminates fabricated from the Continuous Resin Transfer Molding (CRTM) pultrusion process were the focus of this research. The tricot stitch and the 6% vinyl ester matrix cure shrinkage were found to play key roles in the quasi-static and fatigue strength and stiffness properties of these laminates. Laminates tested transverse to the pultrusion axis had greater fiber undulation and maximum of 44% quasi-static strength reduction and 8% stiffness reduction compared with axially tested specimens. While the matrix failure strain was 1.9%, failure strain of these laminates range over 1.91 to 2.08% when tested along the pultrusion axis and as low as 1.29% transverse to the pultrusion axis. Fatigue evaluation, in load control mode, evaluated laminate S-N, stiffness reduction, and residual strength. Measured S-N curves and residual strength curves compared with literature were found most like woven fabric laminates, well below aerospace grade laminates. Residual strength and life analysis using Reifsnider's methodology [43], revealed that the choice of quasi-static strength and stiffness, S-N curve, laminate stiffness reduction, and residual strength shape parameter, J, strongly affect predicted life. Predictions at high fatigue stress/low cycle were more exact than at low stress; the S-N curve was steep initially but at low stress/high cycle was nearly horizontal. The best predictions utilized separate off-axis stiffness reductions of E2 obtained from cross-ply and G12 from angle-ply laminates, the quasi-static strength and stiffness of the laminate predicted, and the average S-N and residual strength curves. / Master of Science

No description available.

Thesis (M.S.) in Civil Engineering--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 125-133).

No description available.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 118 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 117-118).

This work embraces two different manufacturing processes: pultrusion androtational moulding. One (pultrusion) is concerned with manufacture with athermosetting composite while the other is concerned with manufacture of anunfilled thermoplastic. The connecting theme is one of energy usage in manufacturewith these processes. While a large number of comprehensive computer models of pultrusion havebeen generated, most are focussed on the prediction of the temperature andconversion distributions within the profile; by contrast, the analysis presented here isdirected towards the prediction of the duty cycle of the mould heaters as a first stepin recognising the significance of the energy consumed in the process. The results ofthe model are compared with experimental measurements of the duty cycle of anindustrial machine. The nature of this particular investigation was predominantlyapplied and in particular directed towards industrial use. For this reason, the modelwas created in MATLAB, a software package which is relatively more accessible tothe reinforced plastics industry than FE packages. The project involved extensivemodelling and experimentation. It is shown that the line speed could be increased significantly by preheatingthe profile before it enters the die. For example, line speed for one particular profilewas increased from 0.4m/min to 0.5 m/min by using a pre-heater set at 80°C. Thiswork also showed that the specific energy consumption of the process was 0.2kWh/kg to 0.3 kWh/kg; under different line speeds and operating conditions. Thiswas achieved by measuring the duty cycle of the heaters on the die. This increase inline speed means a saving of up to 30 % of the specific energy consumption in thepultrusion. The energy theme continues through the work on rotational moulding. It isshown that the specific energy consumption in rotational moulding can be reducedby up to 70% by direct heating of the mould by using electrical resistance heatersinstead of current method of using hot air to heat the mould. The finite elementmodel showed that this alternative heating method is capable of producing asuniform a heat distribution on the surface of the mould as the current heating systemby using cyclic heating.

Sizings, a thin polymer coating applied to the surface of the carbon fiber before impregnation with the matrix, have been shown to affect the mechanical performance of the composite. These sizings affect the processability of the carbon fiber that translates into a composite with less fiber breakage and improved fiber/matrix adhesion. In addition, the interdiffusion of the sizing and the bulk matrix results in the formation of an interphase. This interphase can alter damage initiation and propagation that can ultimately affect composite performance. The overall objective of the work detailed in this thesis is to ascertain the effects that thermoplastic sizing agents have on composite performance and determine the phenomenological events associated with the effects. All of the thermoplastic sizings had improved processability over the traditional G' sizing. These improvements in processability translated into a composite with less fiber damage and improved surface quality. In addition, all of the thermoplastic sizings outperformed the industrial benchmark sizing G' by at least 25% in static tensile strength, 11% in longitudinal flexure strength, and 30% in short beam shear strength. All moduli were found to be unaffected by the addition of a sizing. The interphase formed in K-90 PVP sized carbon fiber composites was fundamentally predicted from the constitutive properties of K-90 PVP/Derakane™ interdiffusion and fundamental mass transport equations. The K-90 PVP sizing material interdiffusing with the Derakane™ matrix was found to be dissolution controlled. The dissolution diffusion coefficient had an exponential concentration dependence. Fundamental mass transport models were utilized to predict the interphase profile. The predicted K-90 PVP interphase concentration profile displayed steep gradients at the fiber/matrix interface but essentially no gradients at points distant from the fiber surface. The predicted mechanical property profile was essentially flat for the modulus but did show a steep gradient in the strain-to-failure and shrinkage properties. However, the K-90 PVP interphase compared to the unsized/pure Derakane™ interphase showed improvements in strength and strain-to-failure and a reduction in cure shrinkage without significantly affecting the interphase tensile or shear moduli. / Ph. D.

The objective of this study is to design a pultrusion die with a desired temperature profile. Design optimization programs were developed to synthesize the number of cartridge heaters, power input and location of each cartridge heater for a laboratory-scale pultrusion die. This is the first step in developing a pultrusion control process. Before this can be done, a thorough understanding of the pultrusion process is required. The parameters investigated are fiber-resin mixture, degree of curing, production temperature profile and pulling speed. It was found that these parameters are interrelated. / Master of Science